Part I Authentication #

Linux uses PAM (pluggable authentication modules) in the authentication process as a layer that mediates between user and application. PAM modules are available on a system-wide basis, so they can be requested by any application. This chapter describes how the modular authentication mechanism works and how it is configured.

When multiple Unix systems in a network access common resources, it becomes imperative that all user and group identities are the same for all machines in that network. The network should be transparent to users: their environments should not vary, regardless of which machine they are using. This can be done by NIS and NFS services. NFS distributes file systems over a network and is discussed in Chapter 19, Sharing file systems with NFS.

NIS (Network Information Service) can be described as a database-like service that provides access to the contents of /etc/passwd, /etc/shadow, and /etc/group across networks. NIS can also be used for other purposes (making the contents of files like /etc/hosts or /etc/services available, for example), but this is beyond the scope of this introduction. People often refer to NIS as YP, because it works like the network's “yellow pages.”

Whereas Kerberos is used for authentication, LDAP is used for authorization and identification. Both can work together. For more information about LDAP, see Chapter 5, LDAP with 389 Directory Server, and about Kerberos, see Chapter 6, Network authentication with Kerberos.

The Lightweight Directory Access Protocol (LDAP) is a protocol designed to access and maintain information directories. LDAP can be used for tasks such as user and group management, system configuration management, and address management. In SUSE Linux Enterprise Server 15 SP6, the LDAP service is provided by the 389 Directory Server, replacing OpenLDAP.

Kerberos is a network authentication protocol which also provides encryption. This chapter describes how to set up Kerberos and integrate services like LDAP and NFS.

Active Directory* (AD) is a directory-service based on LDAP, Kerberos, and other services. It is used by Microsoft* Windows* to manage resources, services, and people. In a Microsoft Windows network, Active Directory provides information about these objects, restricts access to them, and enforces po…

The RADIUS (Remote Authentication Dial-In User Service) protocol has long been a standard service for manage network access. It provides authentication, authorization and accounting (AAA) for large businesses such as Internet service providers and cellular network providers, and is also popular for …